Mannii or rapae?

[David M]

I've been sent these images from the Montes Universales in NE Spain in early August 2018.

I believe I saw this particular butterfly and my first thoughts were that it was Southern Small White, due to the bold black markings on the apical forewing.

Sadly, the images are insufficiently clear to make out the forked vein (or lack of) on the unf, so does anyone want to pass comment as I really can't be absolutely certain?

[Pieter Vantieghem]

I would say this is P. rapae, summer generation P. mannii would have much bolder discal frontwing markings and still have some more dusting on underside hindwing (although less obvious than in spring). But I do always favour to see upperside markings with this species pair.
The feature of the forked vein is unreliable. I have P. mannii on picture with a forked vein in the frontwing apex.
https://www.flickr.com/photos/161811907 ... 848145575/

[Padfield]

My intuition too is that this is rapae, not least from the scaling on the underside hindwing, as Pieter says.

I'm interested in your forked mannii, Pieter. What evidence do you have this is definitely mannii, not an anomalously dark summer brood rapae?

I never use the fork criterion in the field (because it's so difficult to see with the naked eye) but on examination of photos have found it to correlate in every case. It's a shame if it's not 100% reliable but only to be expected, I guess - so few criteria, on their own, are. In Switzerland I would say it is definitely a strong indicator.

Guy

[David M]

Many, many thanks for this, Pieter/Guy.

Although I was confident when I first saw it that it might be mannii, with each scrutinisation of the images I became less convinced.

As you say, it is too pale on the underside and the fact we didn't see any others is a strong indicator that it was probably rapae, albeit a rather well marked example.

[Pieter Vantieghem]

Hi Guy,
this is the upperside of the same individual (a male), typical moonshaped discal spot with outer edge of the spot concave (rounded in male P. rapae), the discal spot wedged between and almost bursting out of vein 3 & 4 (much smaller in P. rapae), with dusting along the veins from discal spot to outer margin. This is how typical male P. mannii look like in late summer in NW Europe.
https://www.flickr.com/photos/161811907 ... 848145575/

In fact I don't really know who was the first to mention the forked-vein-feature. Lafranchis mentions it in his European guide, in his newer French guide he already "downgraded" this feature only to be valid seen from P. rapae (so fork present = rapae, not present = mannii or rapae) but also from other people I was already told this feature didn't hold, for example Heiner Ziegler (author of a 1990's monograph on P. mannii) answered a question of me regarding this in september 2016 and wrote this on the venation:

Venation of these two species does not help, what Lafranchis writes about P. mannii is nonsense.